The water washing tower has a water retention issue.
Thread Content
Recently, the issue of water remaining in the wash towers in the workshop has become increasingly apparent. The main reason for this is severe scaling on the trays. Therefore, the following issues are brought up for discussion: 1. Is severe scaling on the trays primarily caused by an unreasonable design of the tray bubble structure? Is it necessary to modify the cyclone separators?； 2. Without stopping the operation, by adjusting the water supply distribution to the wash tower – that is, the distribution of water between the tray and the graywater at the bottom of the tower – reducing the water supply to the trays while increasing the water supply at the bottom of the tower. Could this lead to dust accumulation and clogging of the filters in the water separator and the inlet filters of the condensate pump in the conversion section? 3. Is it related to the coal quality and the properties of the coal slurry?
Could the poster please explain what type of process is used in your company’s gasification unit? Is the feed for the gasification unit in the form of lump coal, crushed coal, pulverized coal, or coal slurry? Which company makes the gasification process package? Understanding these will help in discussing the several questions to answer you.
Four-nozzle opposed water-coal slurry gasification technology, East China University of Science and Technology.
Generally speaking, the ash content in the raw gas produced by the water-coal slurry gasification process is much lower than that in the raw gas produced by the pulverized coal gasification process. If you adopt the powder coal gasification process, your washing tower problem will become much more severe.
Based on NOVEL’s experience in participating in technical exchanges regarding the dust removal process packages for raw gas in large-scale gasification plants both domestically and internationally, there are two main reasons for severe scaling on the trays of wash towers. Firstly, it is related to the design and configuration of the upstream cyclone separators; at present, the vast majority of installations in China use traditional standard cyclone separators to remove ash from the gas flow. These separators have low separation efficiency and unstable operation, necessitating technical upgrades by adding internal components ； Secondly, it is also related to the hardness and pH value of the washing soft water; by controlling the parameters of this washing soft water, this issue can be resolved relatively easily.
Regarding the use of cyclone separators to remove dust from gasification units, foreign countries have relatively complete sets of process equipment. It is mainly used for dust and foam removal from raw gas in water-coal slurry gasification (GE Texaco and other similar processes developed through the introduction and adaptation of domestic technologies), pulverized coal gasification (similar processes developed or improved by Shell and other companies), and lump coal crushed coal gasification (Lurgi and other similar processes). The processes introduced domestically or developed through the adaptation and further refinement of existing technologies essentially adopt a piecemeal approach to the dust and foam removal process in raw gas, and all of them have various problems. Abroad, there is a relatively complete set of process equipment: a first-stage cyclone is used to remove most of the larger particles and droplets; a second-stage venturi is employed to wet the smaller dust particles, followed by a cyclone separator to remove the slurry and solid matter; a third-stage venturi is used to wet the finest dust particles, again with a cyclone separator to eliminate any remaining slurry. Finally, a water scrubber together with a wick-type demister is used to remove the trace amounts of slurry present in the gas stream. As a result, the dust and liquid content in the gas entering the conversion unit is 1–3 mg/Nm^3 or even lower. The cyclone separator has been upgraded from a conventional cyclone to a multi-factor cyclone parent/child separation demister, and the demister at the top of the scrubber tower has been upgraded from a conventional wire mesh type to a feather-leaf type demister.
Thank you for your detailed response. Could you provide some basic information regarding the following process: stage 1, where cyclonic separation is used to remove most of the larger particles and droplets; stage 2, where a venturi tube is used to wet the smaller dust particles, followed by cyclonic separation to remove the slurry and solid materials; stage 3, where another venturi tube is used to wet the finest dust particles, with cyclonic separation again used to remove any remaining slurry; and finally, a water scrubber together with a defoamer being used to remove the extremely small amounts of slurry present in the air stream? Thank you so much!
Our company provides technical proposal documents that include the detailed process flow mentioned above, calculations related to process separation, pictures of the models of key equipment, and other details; however, this service is subject to a contract agreement and constitutes a paid professional technical consulting service.
Without stopping the operation, by adjusting the water distribution to the wash tower – that is, the distribution of water between the trays and the graywater at the bottom of the tower – the water supply to the trays is reduced while the water supply at the bottom of the tower is increased, which poses a risk of insufficient washing intensity. Airflows with excessive dust content can cause problems such as blockages in downstream pipelines, leading to a vicious cycle. It is best to control the hardness of the washing water and ensure that its strength meets the requirements of the original process technology.
Without stopping the operation, by adjusting the water distribution to the wash tower – that is, the distribution of water between the trays and the graywater at the bottom of the tower – the water supply to the trays is reduced while the water supply at the bottom of the tower is increased, which poses a risk of insufficient washing intensity. Airflows with excessive dust content can cause problems such as blockages in downstream pipelines, leading to a vicious cycle. It is best to control the hardness of the washing water and ensure that its strength meets the requirements of the original process technology.
Without stopping the operation, by adjusting the water distribution to the wash tower – that is, the distribution of water between the trays and the graywater at the bottom of the tower – the water supply to the trays is reduced while the water supply at the bottom of the tower is increased, which poses a risk of insufficient washing intensity. Airflows with excessive dust content can cause problems such as blockages in downstream pipelines, leading to a vicious cycle. It is best to control the hardness of the washing water and ensure that its strength meets the requirements of the original process technology.